I would like to recommend taking a private tour from Tatiana.
My wife and I visited in summer (2010) and were very pleased with Tatiana's services. With her we entered the museums quickly bypassing the public queue. She is knowledgeable - but doesn't show off by inundating you with endless historical facts and figures as some guides have a tendency to do. We feel she struck a good balance between historical information and interesting stories/anecdotes.
You also have the chance to visit places more off the beaten path. For example as a contrast to the grand palaces Tatiana took us to the former private apartment of a communist leader Kirov. We really enjoyed this visit. I doubt that large groups go there, and think it would be difficult to do independently unless you speak Russian.
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